[RFC PATCH 17/56] x86/bugs: Reset TSA mitigations

David Kaplan
2025-10-13T14:35:34Z

Add function to reset TSA mitigations back to their boot-time defaults.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
---
arch/x86/kernel/cpu/bugs.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index bf5de097e1a9..6a3e079a85fc 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1858,6 +1858,17 @@ static void __init tsa_apply_mitigation(void)
}
}

+#ifdef CONFIG_DYNAMIC_MITIGATIONS
+static void tsa_reset_mitigation(void)
+{
+ setup_clear_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
+ setup_clear_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM);
+ static_branch_disable(&cpu_buf_idle_clear);
+ tsa_mitigation =
+ IS_ENABLED(CONFIG_MITIGATION_TSA) ? TSA_MITIGATION_AUTO : TSA_MITIGATION_NONE;
+}
+#endif
+
#undef pr_fmt
#define pr_fmt(fmt) "Spectre V2 : " fmt

@@ -3978,5 +3989,6 @@ void arch_cpu_reset_mitigations(void)
gds_reset_mitigation();
bhi_reset_mitigation();
its_reset_mitigation();
+ tsa_reset_mitigation();
}
#endif
--
2.34.1